An engine exhaust system typically comprises ductwork with a plurality of duct pieces that are connected together to form conveyance passages for exhaust gasses. For example, a duct piece can be fixed to the exhaust manifold head (and aligned with one or more exhaust ports) and connected to other duct pieces to convey exhaust gas to a vehicle's outlet pipe. If the engine includes an EGR (i.e., exhaust gas recirculation) design, duct pieces can be interconnected to convey exhaust gas back into the air intake line for reintroduction into the combustion chamber. Such a multi-piece construction of the ductwork allows the engine exhaust system to accommodate the thermal expansion-contraction that occurs during engine warm-up, operation, and/or cool-down.
Diesel engine manufacturers conventionally use piston ring type seals in exhaust system applications. The piston ring seals allow for significant relative motion and movement for the exhaust manifold components to thermally expand. However, piston rings are not continuous seals. Piston rings have a cut in them to allow flexibility in the hoop direction. This gap provides a leak path for exhaust gas to leak out of the exhaust system. This leaked exhaust bypasses the catalytic converter, exhaust gas recirculation, and/or particle collection components. As exhaust emissions get tighter and tighter, these small exhaust leaks need to be prevented and all exhaust gas needs to be collected and treated through the exhaust system.